Inhibition of IgG autoantibody-opsonized platelet phagocytosis by red blood cells. RBC opsonized with (A) monoclonal anti-D antibodies (MoAnti-D) IgG3r9B8 (●) or IgG1r9B8 (○), (B) MoAnti-D BRAD3 (●) or BRAD5 (○), (C) MoAnti-D IgG1Rh113 (●) or IgG1Rh178 (○), and (D) RBC opsonized with a mixture of all 6 MoAnti-D (●). The data are presented as the mean percent inhibition (± SD) at the indicated RBC:THP-1 ratios (N = 6) and was calculated as in Figure 1. Statistical significance (P values) by an unpaired t test is shown; all solid symbols were compared with the corresponding nonopsonized RBC inhibition in panel 1B, ★; P < .001.